JP2000105376A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device of an axially symmetric alignment mode having excellent alignment stability for the axial symmetry, high transmittance and quick response. SOLUTION: The liquid crystal layer is divided into plural liquid crystal regions by a projection structure 11 formed on a substrate 10. The liquid crystal molecules 13 in the plural liquid crystal region show negative dielectric anisotropy and aligned perpendicular to the substrate 10 by aligning regulating force of the perpendicular alignment film when no voltage is applied. The projection structure 11 has faces 11a tilted against the surface of the substrate 10, and when voltage is applied, the liquid crystal molecules 13 are axially symmetrically aligned around the axis perpendicular to the surface of the substrate 10. The projection structure 11 has recess structure 11c on its top part 11b, and the liquid crystal molecules 13 on the top part 11b of the projection structure 11 are axially symmetrically aligned by the recess structure 11c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device, and more particularly to a large-screen liquid crystal display device having a wide viewing angle characteristic.

[0002]

2. Description of the Related Art Conventionally, as a display device using an electro-optic effect, a TN (twisted nematic) or STN (super twisted nematic) type liquid crystal display device using a nematic liquid crystal has been used. Techniques for increasing the viewing angle of these liquid crystal display devices have been energetically developed.

One of the techniques for widening the viewing angle of a TN type liquid crystal display device
For example, Japanese Patent Application Laid-Open No. 7-120728 discloses a liquid crystal display device having liquid crystal molecules that are axially symmetrically aligned in a liquid crystal region divided by polymer walls (that is, projecting structures).
So-called ASM (Axially Symmetric)
A liquid crystal display device of an all aligned microcell mode is disclosed. A liquid crystal region substantially surrounded by polymer walls is typically formed for each pixel. Since the liquid crystal molecules of the ASM mode have liquid crystal molecules that are axially symmetrically aligned, the change in contrast is small even when the observer views the liquid crystal display from any direction, that is, has a wide viewing angle characteristic.

Further, as a method of forming the ASM mode liquid crystal display device, a lattice-like projection structure is formed on a substrate, and an axially symmetric alignment is formed by the interaction between the projection structure and liquid crystal molecules. The method is disclosed in JP-A-7-120728. Further, an AS combining a liquid crystal material having negative dielectric anisotropy (N-type liquid crystal) with a vertical alignment film
Japanese Patent Application Laid-Open No. 10-13 / 2009
No. 3206 is disclosed.

On the other hand, as a promising candidate for a large-sized liquid crystal display device, a plasma-addressed liquid crystal display device is being developed. Plasma-addressed liquid crystal display devices, for example,
It is disclosed in Japanese Patent Application Laid-Open No. 1-217396. The plasma addressed liquid crystal display device has a row-shaped discharge channel (plasma channel) surrounded by a substrate, a thin dielectric sheet, and a rib formed between the substrate and the dielectric sheet. The plasma discharge state is switched by switching the voltage applied from the anode electrode and the cathode electrode to the rare gas in the discharge channel. The liquid crystal layer is driven by the voltage of the discharge channel applied to the liquid crystal layer via the thin dielectric layer and the voltage applied to the counter electrode.

However, in the liquid crystal display device disclosed in the above-mentioned publication, the liquid crystal molecules are aligned in one direction, so that there is a problem in the viewing angle characteristics. In order to solve this problem, Japanese Patent Application Laid-Open No. 9-197384 discloses that the above-described ASM mode is applied to a plasma addressed liquid crystal display device.
And Japanese Patent Application Laid-Open No. 10-186331.

[0007]

However, the present inventor has found that the liquid crystal display device in which the conventional ASM mode is applied to the plasma addressed liquid crystal display device has the following problems (1) to (3). . (1) Decrease in transmittance In the above-described ASM mode liquid crystal display device, when a black projecting structure (which does not transmit light) is formed, if the projecting structure enters a picture element, the aperture ratio is significantly reduced. Let
Reduce transmission. When a transparent projection structure is used, the above problem does not occur. However, as schematically shown in FIG. 1, the thickness d2 of the liquid crystal layer 2 on the projection structure 1 is reduced. The thickness is smaller than the thickness d1 of the liquid crystal layer 2 in the other region, and the liquid crystal layer 2 on the protruding structure 1 cannot sufficiently contribute to the display, and apparently the transmittance is reduced and the aperture ratio is reduced. Is displayed. This is because the thickness of the liquid crystal layer is designed on the basis of the thickness d1 of the liquid crystal layer in a region where the projection-like structure 1 does not exist, so that the liquid crystal display device is designed.
If the thickness d2 of the liquid crystal layer on the protruding structure 1 is significantly different from d1, the retardation of the liquid crystal layer in that region will deviate from the design value, and the amount of light contributing to display will decrease. (2) Poor stability of axially symmetric alignment (high-speed response, pressing) In the projection-like structure 1 of the conventional example, the portion having the force for regulating the alignment of the liquid crystal molecules is the inclined surface 1a of the projection-like structure. (FIG. 1). Therefore, the top portion 1b of the projection-like structure 1 has almost no alignment regulating force, and the alignment of the liquid crystal molecules becomes unstable. For example, a change in the alignment state of the liquid crystal molecules cannot follow a rapid change in the voltage, a regular alignment state cannot be obtained, and as a result, a rough display is observed.
Further, when an external pressure is locally applied to the liquid crystal cell, the alignment control force on the projection-like structure 1 is small, so that the flow alignment of the liquid crystal molecules occurs, which is observed as a rough display as described above. You. (3) Slow response speed In the case of a conventional plasma addressed liquid crystal display device, a voltage is applied between the liquid crystal layer and a thin dielectric sheet (for example, a glass sheet having a thickness of about 50 μm). The applied voltage depends on the thickness of the liquid crystal layer. When the ASM using the above-mentioned protruding structure is applied to a plasma addressed liquid crystal display device, a voltage is not sufficiently applied to the liquid crystal layer on the protruding structure because the liquid crystal layer on the protruding structure is thin. Therefore, the response speed of the liquid crystal layer on the top portion of the projection-like structure becomes extremely slow, and the response speed of the halftone is reduced as a whole.

Further, as described above, since there is almost no alignment regulating force on the top portion of the protruding structure, the alignment of liquid crystal molecules after voltage application is gradually changed, and as a result, the response speed is reduced. Would. This phenomenon will be described with reference to FIGS.

In the state where no voltage is applied, as shown in FIG. 2A, the liquid crystal molecules 3 are on all surfaces (the vertical alignment film is not shown).
Oriented perpendicular to When voltage is applied to the liquid crystal layer,
First, as shown in FIG. 2B, the liquid crystal molecules 3 start to fall in random directions. At this time, the liquid crystal molecules 3 near the inclined side surface 1a of the projecting structure 1 are affected by the side surface 1a.
It falls down into a region (sub-pixel) substantially surrounded by the protruding structure 1 (hatched portion in FIG. 2B). Next, as shown in FIG. 2C, the liquid crystal molecules 3 in the sub-pixel have an energetically stable axially symmetric alignment due to the interaction with the liquid crystal molecules 3 near the side surface 1a of the protruding structure 1. (The hatched portion in FIG. 2C). Thereafter, as shown in FIG. 3D, the interaction of the liquid crystal molecules 3 on the tops of the protruding structures 11 changes due to the interaction with the liquid crystal molecules 3 in the sub-pixels which are axially symmetrically aligned. Since the orientation of the liquid crystal molecules 3 in the four sub-pixels of the projecting structure 11 is equally affected, the liquid crystal molecules 3 on the top of the projecting structure 11 are also axially symmetrically oriented.

As described above, since the alignment of the liquid crystal molecules 3 changes stepwise, the response speed of the entire picture element is reduced. Further, as described above, since the alignment regulating force on the top of the projection-like structure 1 is very small, the alignment is easily disturbed by the influence of the pressure from the outside of the display panel, and the disordered alignment is restored. This requires a longer time in comparison with the liquid crystal molecules 3 in other regions.

In order to prevent the above phenomenon, a technique for fixing the alignment of liquid crystal molecules by a monomer is disclosed in Japanese Patent Application Laid-Open No. 7-12072.
No. 8 discloses this. In the alignment fixing technique disclosed in the above publication, a mixture of a liquid crystal material and a photocurable monomer is added to a cell formed using a substrate having a projecting structure, and a voltage is applied to form an axially symmetric alignment state. Let me
An alignment fixing layer is formed by reacting a monomer present in the cell with ultraviolet rays, thereby fixing the axially symmetric alignment state of the liquid crystal molecules. By reducing the amount of monomer,
The vertical alignment when no voltage is applied can be maintained. However, when this method is used, an extra step for forming the alignment fixed layer is required, which leads to an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an axisymmetric alignment mode liquid crystal display device which is excellent in axisymmetric alignment stability, has a higher transmissivity, and has a higher response speed. The purpose is to provide.

[0013]

A liquid crystal display device according to the present invention comprises a first substrate, a second substrate, and a liquid crystal layer sandwiched between the first and second substrates. The first substrate has a projection structure and a vertical alignment layer provided on the liquid crystal layer side, and the liquid crystal layer has a plurality of liquid crystal regions divided by the projection structure. A liquid crystal display device, wherein the liquid crystal molecules in the plurality of liquid crystal regions have negative dielectric anisotropy and are axially symmetrically aligned around an axis perpendicular to the surface of the first substrate when voltage is applied, The projecting structure has a surface inclined with respect to the surface of the first substrate, and has a concave structure at a top portion, thereby achieving the above object.

[0014] The depth of the concave structure may be smaller than the height of the protruding structure. Preferably, the concave structure has a surface inclined with respect to the surface of the first substrate, and an angle of the inclined surface of the concave structure with respect to the surface of the first substrate is 45 ° or less.

The projections may be arranged in a lattice pattern, or the projections may be arranged in a checkered pattern.

The second substrate is a plasma cell substrate having a row-shaped discharge channel surrounded by a substrate, a dielectric sheet, and a rib formed between the substrate and the dielectric sheet, The protruding structure may be formed between the first substrate and the dielectric sheet.

The operation of the present invention will be described below.

The projection structure in the liquid crystal display device of the present invention divides the liquid crystal layer into a plurality of liquid crystal regions. Since the liquid crystal molecules in the plurality of liquid crystal regions have negative dielectric anisotropy, the liquid crystal molecules are vertically aligned with the substrate when no voltage is applied by the alignment regulating force of the vertical alignment film. The protruding structure has a surface inclined with respect to the surface of the substrate, and when voltage is applied, acts so that the liquid crystal molecules are axially symmetrically aligned around an axis perpendicular to the surface of the substrate. Further, the projecting structure according to the present invention has a concave structure at the top, and the concave structure has an alignment regulating force for axially symmetrically aligning the liquid crystal molecules at the top of the projecting structure.
Therefore, in a conventional ASM mode liquid crystal display device,
Since the liquid crystal layer on the projecting structure that has not been effectively used for display can be effectively used for display, the transmittance of the liquid crystal display device is improved.

When the depth of the concave structure is smaller than the height of the protruding structure, a slope for determining the alignment regulating force of the liquid crystal molecules is formed continuously (to increase the area) in the concave structure. Thereby, the alignment regulating force can be increased. When the angle of the inclined surface of the projection structure with respect to the surface of the substrate is 45 ° or less, the liquid crystal molecules can be more efficiently axisymmetrically aligned.

By forming the projection-like structures in a lattice pattern, it is possible to form a liquid crystal region having an axially symmetric orientation corresponding to the picture element. Further, by arranging the projecting structures in a checkered pattern, it is possible to suppress a decrease in transmittance even when the projecting structures are formed in a liquid crystal region having a fine pitch.

By applying the liquid crystal display device of the present invention to a plasma addressed liquid crystal display device having a row discharge channel, the transmittance, response speed and alignment stability of the conventional ASM mode plasma addressed liquid crystal display device can be improved. Can be greatly improved.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the problem of the conventional ASM mode liquid crystal display device is that the top portion of the protruding structure 1 (typically formed as a polymer wall) shown in FIG. The inventor of the present application has found out that 1b does not have a sufficient alignment regulating force. In the ASM mode liquid crystal display device according to the present invention, the top portion 11b of the protruding structure 11 formed on the liquid crystal layer side surface of at least one of the pair of substrates 10 sandwiching the liquid crystal layer has a concave structure 11c. . For example, in the case of a plasma-addressed liquid crystal display device, the substrate on which the protruding structure 10 is formed may be a thin dielectric sheet constituting the plasma-addressed substrate, or may be the surface of the opposing substrate facing the liquid crystal layer. You may. Hereinafter, the structure and characteristics of the present invention will be described in detail.

(Adjustment Effect of Alignment by Concave Structure on Top of Projection Structure) FIG. 3 shows a projection structure 11 according to the present invention. The protruding structure 11 formed on the substrate 10 has an inclined surface 11a (inclination angle α) and a top portion 1a.
1b has a concave structure 11c. The concave structure 1c preferably has a slope 11d (tilt angle β).

Such a concave structure 11c is formed on the top portion 11b.
When a voltage is applied to the liquid crystal layer on the substrate having the projecting structure 11 formed on the substrate, the inclined surface 11 of the projecting structure 11
While the liquid crystal molecules 13 on d fall, the liquid crystal molecules 13 on the slope 11d of the concave structure 11c fall toward the inside of the concave structure 11c. The inner surface 11d of the concave structure 11c is
It is more effective to regulate the orientation than to be stood perpendicular to the surface of 0, and the inclination angle β is 45 °.
It is more preferred that: Because the concave structure 1
When the inner surface 11d of 1c is a vertical surface, the liquid crystal molecules 13 are oriented perpendicular to the top portion 11b of the protruding structure 11, so that the liquid crystal molecules 13 are parallel to the substrate even when a voltage is applied. There is little effect of tilting in any direction.

Preferably, the angle of inclination α is in the range of about 3 ° to about 45 °. When the tilt angle α exceeds about 45 °, the change in the orientation of the liquid crystal molecules due to the application of a voltage (change in the tilt angle)
, The effect of regulating the orientation by the inclined surface may not be sufficiently obtained. The inclination angle is about 3
When the angle is smaller than °, the effect of the inclined surface is not sufficiently exhibited, and the liquid crystal molecules in the region (sub-pixel) substantially surrounded by the projection-like structure 11 do not form an axially symmetric alignment, and as a result, In some cases, the display may have a feeling.

The concave structure 1 of the projecting structure 11 according to the present invention
The alignment control effect of 1c is particularly remarkable in a plasma addressed liquid crystal display device. FIG. 4A schematically shows an example in which the present invention is applied to a plasma addressed liquid crystal display device.

The plasma addressed liquid crystal display device 100 shown in FIG. 4A modulates incident light into outgoing light in accordance with a pixel signal to display a pixel, and a plasma for scanning (addressing) a pixel. It has a flat panel structure composed of the cell substrate 100b. Display cell 1
00a and the plasma cell substrate 100b share the dielectric sheet 53. The dielectric sheet 53 is used for the display cell 10.
Oa functions as a lower substrate and also functions as an upper substrate of the plasma cell substrate 100b.

The plasma cell substrate 100b includes a substrate 55
And a dielectric sheet 53 and a rib 57,
It has discharge channels 65 arranged in a row, and sequentially generates a plasma discharge to scan the display cell 100a line-sequentially.
The discharge channel 65 has an anode electrode A and a cathode electrode K in a row space. Although not shown in the figure,
Needless to say, a power supply circuit for applying a voltage to the anode electrode A and the cathode electrode K to generate plasma discharge, a scanning circuit for controlling scanning, and the like are separately provided. This plasma addressed liquid crystal device 10
A component provided for a conventional plasma addressed liquid crystal device may be used as a component for driving 0.

The display cell 100a has signal electrodes 70 arranged in a column so as to be substantially orthogonal to the discharge channels 65 arranged in a row direction, and defines a pixel at an intersection with the discharge channel 65. By applying a voltage to the cathode electrode K, a plasma discharge is generated in the discharge channel 65, and the potential of the dielectric sheet 53 on the liquid crystal layer 60 side becomes equal to the potential of the anode A. As a result, a data signal (image signal) is applied to both sides of the liquid crystal layer 60 and the dielectric sheet 53. By performing the plasma discharge for each discharge channel 65, that is, in a line-sequential manner, a data signal is applied line-sequentially to the liquid crystal layer 60 in a display region where the discharge channel 65 and the signal electrode 70 intersect, and display is performed. Done.

The plasma cell substrate 100b is
7. A glass substrate 55 provided with an anode electrode A and a cathode electrode K is joined to a dielectric sheet 53 from below. The display cell 100a is provided with the signal electrode 7
Glass substrate 7 on which a polymer wall (not shown) is provided.
2 is joined to the dielectric sheet 53 from above. The gap between the glass substrate 72 and the dielectric sheet 53 (thickness of the liquid crystal layer 60: cell gap) is determined by the protrusions 11 and the columnar protrusions 90 provided on a part of the protrusions 11. Stipulated by The columnar projections 90 are formed so as to be disposed immediately above the regions of the base color filter layer 73 where the black matrix (not shown) is formed. Of course, the signal electrode 70 may be formed on the protruding structure 11. Substrate 72 on which signal electrode 70, protruding structure 11, and columnar protrusion 90 are formed, and dielectric sheet 5
A vertical alignment film (not shown) is formed on the surface of the third liquid crystal layer 60 side.

When the present invention is applied to a plasma-addressed liquid crystal display device, the thickness of the projecting structure 11 particularly affects display characteristics. Referring to FIGS. 4A and 4B, when the height of the protruding structure 11 in the above-described plasma-addressed liquid crystal display device 100 is reduced, the voltage _VLC applied to the liquid crystal layer 60 at this portion is different. Will be described.

Ε _LC , ε _P , and ε _g are the liquid crystal layer 6
0, the dielectric constant of the protruding structure 11, the dielectric sheet 53,
d _LC , d _P , d _g are the respective thicknesses (d = d _LC +
d _P ). Since the dielectric constant is a value specific to each material, when the height d _P of the projecting structure 11 is reduced, the thickness d _LC of the liquid crystal layer on the projecting structure 11 becomes relatively small. Thus, the voltage applied to the liquid crystal layer 60 increases. The lower the height of the protruding structure 11, the more the protruding structure 11
The voltage applied to the upper liquid crystal layer 60 approaches the voltage applied to the portion having the liquid crystal molecules whose axial symmetry is regulated by the protrusions 11 in the liquid crystal region 80a. Therefore, as shown in FIG. 5, in the plasma addressed liquid crystal display device, a cell (セ ル) having a thick liquid crystal layer 60 is driven at a lower voltage than a cell (◆) having a thin liquid crystal layer 60.

When the present invention is applied to a plasma-addressed liquid crystal display device, since the projecting structure 11 has a concave structure 11c at the top, the liquid crystal layer 60 has a thick liquid crystal in the concave structure 11c of the projecting structure 11. Molecules respond (change orientation) at relatively low voltages. Therefore, the liquid crystal molecules on the top of the protruding structure 11 can contribute to display.

Further, the above-mentioned effect works advantageously on the response speed of liquid crystal molecules in halftone display. That is,
Generally, a liquid crystal display device using a nematic liquid crystal material has a problem that a response speed in a halftone is slow and a fast moving image cannot be sufficiently displayed. However, in a plasma addressed liquid crystal display device to which the present invention is applied,
The liquid crystal molecules in the concave structure 11c have an intermediate voltage between the voltage at which the liquid crystal molecules move in the region 80a substantially surrounded by the projection-like structure 11 and the voltage at which the liquid crystal molecules move on the inner surface 11d of the concave structure 11c. Since it moves, apparently the response speed in the halftone display increases. (Concave Structure) FIG. 6 shows an example of a two-dimensional arrangement (arrangement on the surface of the substrate) of the concave structure. As shown in FIG. 6, the protrusions 11 can be formed so as to penetrate a part of the top portion 11b of the protruding structure 11 arranged in a grid. With this structure, the liquid crystal molecules can be axially symmetrically aligned by the alignment regulating force from the four inner surfaces of the concave structure 11c formed on the top portion 11b of the projection-like structure 11 to the liquid crystal molecules 13. Such a shape in which a part of the projecting structure 11 is hollowed out has a top portion 11 of the projecting structure 11 as shown in FIG.
b may be continuously hollowed out or partially hollowed out. Further, when the pitch P of the lattice of the protruding structures 11 is small, the resolution of the photomask in the photolithography process for forming the protruding structures 11 is not good,
When viewed from the normal direction of the substrate, the area of the projecting structure 11 is larger than the area of the opening (the area surrounded by the projecting structure), and the occupation ratio of the region where the thickness of the liquid crystal layer is large. Becomes large, and as a result, the transmittance may be reduced. When a structure with a fine pitch is formed as described above, it is preferable that the projecting structures 11 be two-dimensionally arranged in a checkered pattern (described later with reference to FIG. 12). The present invention is effective also in such a checkered pattern arrangement, and the concave structure 1
1c can be formed. By forming the concave structure 11c on the top portion 11b of the protruding structure 11, the ratio of the region where the thickness of the liquid crystal layer is large can be increased, so that a decrease in transmittance can be prevented.

That is, according to the present invention, even if the projecting structure 11 is formed in a picture element, the transmittance is not greatly reduced. Therefore, in a liquid crystal display device having a large picture element, the transmittance is reduced even when the projection-like structure 11 is formed in the picture element and one picture element is divided to form a plurality of axially symmetric alignment regions in the picture element. Never do. At this time, it is preferable that the divided structure is rectangular, and the pitch of the projecting structures 11 formed on the color filter substrate and the pitch of the discharge channels are matched. When the pitch of the protrusion-like structures 11 and the pitch of the discharge channels are shifted, a periodic change (moire) in the transmittance occurs. Further, concave structures 11c having different sizes may be formed.

As described above, the inner surface 11d of the concave structure 11c is preferably a gentle slope having an inclination angle β of about 70 ° or less and about 5 ° or more than perpendicular to the substrate. If the tilt angle β is smaller than about 5 °, it is not possible to sufficiently control the alignment of the liquid crystal molecules 13. Also, the inclination angle β is about 70
When the angle exceeds °, a deep concave structure 11c is required to obtain a sufficient alignment regulating force. Also, the depth hc of the concave structure 11c
8B does not necessarily have to match the height h of the protruding structure 11 as shown in FIG. 8B, and may be smaller than the height h of the protruding structure 11 as shown in FIG. It may be small.
When the depth hc of the concave structure 11c is smaller than the height h of the projection-like structure 11, a slope that determines the alignment regulating force of the liquid crystal molecules is formed continuously (to increase the area) in the concave structure. Thereby, the alignment regulating force can be increased.

The transparent electrode for applying a voltage to the liquid crystal layer may be formed on the surface of the projecting structure 11, or may be formed below the projecting structure. When a transparent electrode is formed under the protruding structure 11, a voltage is applied to the liquid crystal layer via the protruding structure 11, and it is necessary to increase the driving voltage. It is preferable to form 11 low. The height h of the protruding structure 11 is preferably in a range from about 0.3 μm to about 2 μm. If the height is less than about 0.3 μm, it is difficult to control the height, and the protrusions 11 having a uniform height cannot be formed, and display unevenness occurs. As the transparent electrode, a material generally used in a liquid crystal display device can be used, and indium tin oxide (I
TO), Nesa film and the like can be used.

The vertical alignment film is preferably formed on the transparent electrode so as to cover the protruding structure 11 having the concave structure 11c. As the vertical alignment film, for example, JALS-
204 (manufactured by Nippon Synthetic Rubber Co., Ltd.) can be used.

(Method of Forming Concave Structure) As a method of forming the protruding structure having the concave structure, it is preferable to use a photolithography technique using a resist material. In particular, as shown in FIG. 9, in forming the concave structure 21 having an inclined surface, a distance (proxy gap) g between the photomask 20 and the substrate 10 on which the resist layer 21 'is formed may be increased (see FIG. 9 (b)). )), The gap between the light-shielding portions 20a of the photomask portion corresponding to the concave structures 21c (in the case of forming a projecting structure using a positive resist) is reduced so as not to be clearly resolved (FIG. a)), it can be formed by setting the development time to be over.

(Fixation of Axisymmetric Orientation) The stability of the axisymmetric alignment state formed by applying a voltage to the liquid crystal layer differs depending on the size of the region surrounded by the concave structure. In particular, even if an axially symmetric alignment state of liquid crystal molecules is once formed, a flow alignment may be formed by external pressure or the like. In such a case, a polymer stabilizing technique using a photocurable monomer can be applied to stabilize the alignment state of the liquid crystal molecules. That is, a mixture of a liquid crystal material and a photocurable monomer is added to a cell formed using a substrate having a concave structure, and a predetermined voltage is applied to form an axially symmetric alignment state. Is reacted and cured to form an alignment stabilizing layer to fix the alignment state of the liquid crystal molecules. By reducing the amount of the photocurable monomer, it is possible to maintain the vertical alignment when no voltage is applied.

As the liquid crystal material, for example, an N-type liquid crystal material (Δε = −4.0, Δn = 0.08, and a chiral agent may be added if necessary) can be used. In addition, as the photocurable monomer, for example, acrylate, methacrylate, styrene, and derivatives thereof can be used.

(Embodiment 1) In this embodiment, a plasma addressed liquid crystal display device having the same structure as the plasma addressed liquid crystal display device 100 shown in FIG. 4 was manufactured. The arrangement of the protruding structures 31 in the present embodiment will be described with reference to FIG.

Color filter layer (R, G, B and BM)
Was formed on the substrate 30 on which was formed a photo-lithography technique. The protruding structure 11 (having a height of about 1 μm) having a concave structure 31c at the top was formed. The width w of the concave structure 31c was about 10 μm, and the inclination angle β of the inner surface 31d of the concave structure 31c was about 20 °. The inclination angle α is about 30 °, the height of the protruding structure is about 1.0 μm, the depth of the concave structure is about 0.5 μm,
The size of the picture element was about 140 μm × about 140 μm. On the obtained substrate, an ITO layer (not shown) to be a transparent electrode was further formed by a sputtering method, and the ITO layer was etched to the width of a picture element to form a transparent electrode. Further, a columnar structure (not shown) having a height of about 5 μm was formed discretely on a BM (black mask) of this substrate to form a specer. Projection structure 3
The cell thickness of the region surrounded by No. 1 was about 6 μm. Further, a vertical alignment film was applied on the obtained substrate to complete a color filter substrate.

On the other hand, a vertical alignment film was applied on a dielectric sheet of a plasma cell substrate similar to the plasma cell substrate 100b in FIG. 4 to complete the plasma cell substrate.

The two substrates thus formed were laminated to form a cell.
A liquid crystal material having a negative dielectric anisotropy (Δ
(ε = −4.0, Δn = 0.08) and a photocurable monomer represented by the following chemical formula were injected. In addition, Irgacure 184 was used as a photoinitiator.

[0046]

Embedded image

When a voltage was applied to the formed cell, formation of an axially symmetric orientation was confirmed by observation with a polarizing microscope. At this time, a thin axially symmetric orientation was similarly formed on the protruding structure 31 (inside the concave structure 31c). FIG. 11 shows viewing angle characteristics of the obtained liquid crystal display cell. As shown in FIG.
At almost all azimuths (Ψ), a contrast ratio of 10: 1 was obtained in a range of a viewing angle (θ) of 60 ° or less.

(Embodiment 2) In this embodiment, as shown in FIG. 12, the concave structure 41 is further subdivided and arranged two-dimensionally in a checkered pattern. A liquid crystal material to which the photocurable monomer was not added was used as the liquid crystal material. Other configurations are the same as those of the first embodiment. A liquid crystal material was put into the obtained liquid crystal cell to complete the cell.

Also in the liquid crystal cell of this embodiment, an axially symmetric alignment is formed on the protruding structure 41 when a voltage is applied.
Wide viewing angle characteristics were obtained as in the first embodiment. In order to stabilize the alignment without using the polymass-visualizing technique using a monomer as described above, the pitch from the concave structure 41 to the concave structure 41 is preferably about 60 μm or less, and more preferably about 30 μm or less. preferable. In such a subdivided structure, the alignment regulating force from the concave structure 41 is strong and spreads over the entire liquid crystal layer, so that the axially symmetric alignment can be fixed without using a monomer. In fact, even when the formed cell was operated at a high speed, the change in the orientation of the liquid crystal molecules was sufficiently fast, and a good display was obtained.

(Comparative Example 1) On the same color filter substrate as in Embodiment 1, instead of the concave structure 31, a grid-like projection structure (having no concave structure) having a height of about 3 μm was formed. After forming the transparent electrode thereon, a columnar structure of about 3 μm was formed as a spacer. As in the first embodiment, a liquid crystal material containing a monomer was used. Other configurations are
The same as in the first embodiment. The characteristics of the obtained liquid crystal cell are shown in Table 1 below together with the characteristics of the liquid crystal cell of the embodiment.

[0051]

[Table 1] Embodiment 1 Embodiment 2 Comparative example : transmittance ratio at 80 V 1.08-10 V → 80 V Response time 55 ms 58 ms 54 ms

As shown in Table 1, in the comparative example, the transmittance is low because the liquid crystal molecules on the protruding structure do not sufficiently operate with respect to the voltage. In Embodiments 1 and 2, a concave structure is formed at the top of the protruding structure, and a sufficient voltage is also applied to the liquid crystal layer on the top of the protruding structure. Therefore, the transmittance is increased at a relatively low voltage, so that the transmittance is improved as a whole. Further, in the second embodiment, a response speed similar to that of the first embodiment was obtained regardless of not using the alignment fixing effect of the monomer.

In the above embodiment, an example is shown in which the present invention is applied to a plasma addressed liquid crystal display device.
The present invention is not limited to this, and can be applied to an active matrix type liquid crystal display device and a simple matrix type liquid crystal display device.

[0054]

As described above, the projecting structure in the liquid crystal display device of the present invention has a concave structure at the top, and the concave structure aligns the liquid crystal molecules at the top of the projecting structure with axisymmetric alignment. It has an alignment regulating force that causes the alignment. Therefore, in the conventional ASM mode liquid crystal display device, the liquid crystal layer on the protruding structure, which has not been effectively used for display, can be effectively used for display, so that the transmittance of the liquid crystal display device is improved and the response speed is improved. Can be improved. Furthermore, the stability of the axisymmetric orientation is excellent, and a stable axisymmetric orientation can be realized even when an external pressure is applied or during high-speed switching.

The liquid crystal display device of the present invention has excellent viewing angle characteristics and is suitable for a large-sized liquid crystal display device, particularly, a plasma addressed liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a protruding structure used in a conventional AMS mode liquid crystal display device.

FIG. 2 is a diagram schematically showing an alignment state of liquid crystal molecules by a projection structure used in a conventional ASM mode liquid crystal display device. (A) is a state where no voltage is applied, (b) to (d)
Shows changes in the orientation of liquid crystal molecules after voltage application in three stages in time series.

FIG. 3 is a schematic diagram for explaining alignment control of liquid crystal molecules by a concave structure of a projection-like structure according to the present invention.

FIG. 4A is a cross-sectional view illustrating a plasma addressed liquid crystal display device according to an embodiment of the present invention. (B) is a diagram showing an equivalent circuit thereof.

FIG. 5 is a graph for explaining a difference in a voltage-transmittance curve depending on a thickness of a liquid crystal layer.

FIG. 6 is a schematic view showing an example of a two-dimensional arrangement of protrusions according to the present invention.

FIG. 7 is a schematic view showing another example of the two-dimensional arrangement of the projecting structures according to the present invention.

FIG. 8 is a sectional view of a protruding structure according to the present invention.
(A) shows an example where the depth of the concave structure is smaller than the height of the protruding structure, and (b) shows an example where the depth of the concave structure is the same as the height of the protruding structure.

FIG. 9 is a schematic view illustrating a method for forming a projection-like structure according to the present invention.

FIG. 10 is a diagram showing a two-dimensional arrangement (lattice-like arrangement) of the protruding structures according to the first embodiment.

FIG. 11 is an iso-contrast diagram showing viewing angle characteristics of the ASM-mode plasma addressed liquid crystal display device formed in the first embodiment.

FIG. 12 is a diagram showing a two-dimensional arrangement (checkerboard arrangement) of the projecting structures according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 11 Projection structure 11a Slope of projection structure 11b Top part of projection structure 11c Depression structure of projection structure 11d Slope of depression structure 13 Liquid crystal molecule α Slope angle of projection structure β Depression structure Slope angle

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nao Kurihara 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Masato Imai 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Soniー Inc. F term (reference) 2H090 HA02 HA05 HA07 HA15 HB07X HB07Y HB16Y HC11 HD06 JA03 JC03 KA04 KA17 LA01 LA15 LA16 MA01 MB08 MB14

Claims (6)

[Claims] A first substrate, a second substrate, and a liquid crystal layer sandwiched between the first and second substrates; the first substrate includes a protruding structure; A vertical alignment layer provided on the liquid crystal layer side, wherein the liquid crystal layer has a plurality of liquid crystal regions divided by the protrusions, and the liquid crystal molecules in the plurality of liquid crystal regions are negative. A liquid crystal display device having a dielectric anisotropy of, and being axially symmetrically aligned around an axis perpendicular to the surface of the first substrate when a voltage is applied, wherein the projection-like structure is formed on the first substrate A liquid crystal display device having a surface inclined with respect to the surface of the liquid crystal display and having a concave structure at a top portion. 2. The liquid crystal display device according to claim 1, wherein a depth of the concave structure is smaller than a height of the protruding structure. 3. The concave structure has a surface inclined with respect to the surface of the first substrate, and an angle of the inclined surface of the concave structure with respect to the surface of the first substrate is 45 ° or less. The liquid crystal display device according to claim 1. 4. The liquid crystal display device according to claim 1, wherein the protrusion-like structures are arranged in a lattice. 5. The liquid crystal display device according to claim 1, wherein the projecting structures are arranged in a checkered pattern. 6. The plasma cell substrate, wherein the second substrate includes a row and a discharge channel surrounded by a substrate, a dielectric sheet, and a rib formed between the substrate and the dielectric sheet. 6. The liquid crystal display device according to claim 1, wherein said projecting structure is formed between said first substrate and said dielectric sheet.